The best advice I could give is have a search
There's been lots of threads regarding this very question and too many answers to post here....
In brief, treat it as a V70 with extra bits. The AWD is expensive to fix, the suspension is expensive if it's 4C, otherwise standard S60/V70 things to look for
Tip: don't go for pre 2003 no matter how good a deal it looks.
2003 to 2005 will be a 163 D5 and does mid 40's to the gallon
2005 to 2007 will be a 185 D5 and does mid 30's.
Autos a couple of mpg less.